Study Design
Since May 2020, mixed plastic collection in Muttenz has been carried out as a pilot project using 35-liter bags for dry waste collection, as requested by the municipal assembly. Carbotech AG was commissioned to conduct a life cycle assessment study specifically for the Muttenz collection to evaluate the pilot phase. Raymond Schelker, an expert at realcycle GmbH (formerly REDILO GmbH), organized and carried out the manual sorting and analysis of the collection bags.
In principle, the study should answer the following questions:
- Is the separate plastic collection in Muttenz worthwhile from an ecological point of view?
- Is the separate plastic collection in Muttenz worthwhile from an economic point of view?
- Do other scenarios (drop-off instead of pick-up collection, other recycling methods) have a higher ecological benefit than the current scenario?
In order to answer these questions, a separate analysis of the plastic collection bags in Muttenz was carried out. On three collection days, 50 plastic collection bags each were manually sorted, assigned to different plastic fractions and weighed. The quantities and the sorted types of plastic served as the basis for the life cycle assessment calculation. The environmental impacts were assessed using the method of ecological scarcity (MöK). The incineration of the plastics in the Basel waste incineration plant (KVA) served as a reference scenario. The environmental benefit is expressed as a saving of environmental impact points (UBP).
Results of Carbotech's life cycle assessment study
The results of the sorting process show that the quality of the collection is very good. The collection bags contained only 1.5% foreign matter. However, 60% of the materials could not be assigned to a specific type of plastic, and experience shows that around 25% of these may contain problematic additives (plasticizers, flame retardants, stabilizers). These materials can be found in office supplies or garden furniture, for example, but also in children's toys. These materials are problematic in recycling because they remain in the material cycle and can thus enter the environment.
Based on the scenarios examined in the life cycle assessment study (drop-off or pick-up collection, disposal of residual materials in a cement plant or in a waste-to-energy plant), the assumptions made result in varying degrees of ecological benefit from plastic collection in Muttenz. Recycling the residual materials in a cement plant yields a higher ecological benefit than thermal recycling in the Basel waste-to-energy plant. On average, 75% of the residual materials are recycled for energy in cement plants and 25% in waste incineration plants. The plastic collection in Muttenz results in an environmental benefit of approximately 1.35 million UBP per ton.
What does this ecological benefit mean for the population of Muttenz?
For comparison: If a family of four in Muttenz collects plastics for a year and fills a 35-liter bag every four weeks, they save approximately 25,000 UBP in that year. The same saving could be achieved by the family by foregoing the consumption of 220 grams of beef (55 grams/person) or a car journey of just under 50 km. With the separate collection of plastics, an extremely modest ecological benefit can be achieved, which would answer the first question.
The cost analysis of plastic collection in Muttenz shows an annual deficit of around CHF 40,000, as only 45% of the costs are covered by the sale of collection bags. To cover the full costs, the price per bag would have to be doubled. The eco-efficiency of the collection, measured as the ratio of ecological benefit to cost, is low compared to other recycling systems such as PET bottles or aluminum cans. This means that high costs are incurred to reduce relatively little environmental impact.
In addition, the method of ecological scarcity was applied. It assesses the environmental impact by determining environmental impact points (UBP). The plastic collection in Muttenz does achieve an ecological benefit, but it remains low. Alternative collection scenarios such as bring systems or other recovery routes do not show a significantly higher ecological advantage. Despite the possible utilization of the plastics in the cement plant, the plastic collection remains economically loss-making and has a low eco-efficiency.
The entire study can be read here.